0 Assigned ID: 4329 ----- Attempting Submission 1 (Wed May 24 13:49:22 GMT 2023) ----- HST Phase I Proposal 4329 successfully submitted. Receipt: # 4329-1 ----- Attempting Submission 2 (Wed May 24 18:25:16 GMT 2023) ----- HST Phase I Proposal 4329 successfully submitted. Receipt: # 4329-2 Disruptive is a required field. This target is not used in this proposal. Added longer observing windows for visits 07 and 08. -1050290006 ----- Attempting Submission 1 (Wed Sep 13 14:47:07 GMT 2023) ----- ----- Attempting Submission 2 (Fri Sep 05 19:22:29 GMT 2025) ----- ----- Attempting Submission 3 (Mon Sep 08 13:07:51 GMT 2025) ----- I believe the number of disruptive interruptions should be 0 but I was not able to change this myself. Identifying a New Source of r-Process Nucleosynthesis with HST The origin of the Universe's heavy r-process elements is a fundamental issue which affects chemical enrichment across cosmic time and the development of complex life. It is now confirmed that neutron star mergers are responsible for at least some of the r-process budget, but there is gaining observational and theoretical support for an additional and faster production channel: the core-collapse of rapidly-rotating, massive stars. In particular, energetic supernovae with associated long-duration gamma-ray bursts (GRB-SNe) are the strongest candidates for a fast channel. Here, their massive neutronized accretion disks mix with the outer, Ni-dominated ejecta producing dramatic reddening at late times (~50-200 days). Even for the most nearby events, HST is necessary to detect the SN at these epochs when the color of an r-process enriched SN will be distinguishable from an event with no r-process, especially against the background light of a star-forming host galaxy. Yet, as these GRB-SNe r-process models gain traction, no tailored observations with the relevant sensitivity or wavelength coverage exist. We propose a first-of-its-kind study to monitor the late-time evolution of one nearby (z<0.3) GRB-SN as a crucial test of current models. We will obtain 12 HST orbits over 5 epochs in F606W and F160W. The detection of r-process nucleosynthesis in a GRB-SN would be transformative for our understanding of when and where heavy elements enter galaxies like our Milky Way. Given both the long time baseline and rarity of neary LGRBs, we request long-term and carry-over status. This is a non-disruptive target-of-opportunity proposal with long-term and carry-over status. This proposal is for 12 orbits (8 orbits awarded in Cycle 31, 4 in Cycle 32) of HST imaging of a nearby GRB supernova (SN), a promising but untested site to observe the formation of elements via rapid neutron capture (r-process) nucleosynthesis. These observations will observe the SN's color evolution by observing contemporaneously in one optical (F606W) filter and one near-IR (F160W) filter over ~50 - 600 days following the GRB, when ground-based telescopes are no longer sensitive to the SN's expected brightness. Observations will be obtained across 5 visits, with the first 4 visits consisting of one orbit each of WFC3/UVIS F606W and WFC3/IR F160W imaging. The final visit will be 2 orbits in each filter in order to provide a deep template for image subtraction with earlier epochs, intended to remove host galaxy light contamination. PI Jillian Rastinejad (Northwestern) is a 4th year PhD student with extensive experience triggering large-aperture ground-based optical-near-IR facilities following GRBs. The data in this proposal will support at least one chapter of her thesis on uncovering r-process signatures in the counterparts to GRBs. Co-Is Prof. Andrew Levan (Radboud), Prof. Wen-fai Fong (Northwestern) and Prof. Nial Tanvir (Leicester) have PI'd several past HST programs to follow GRBs and will provide scientific and technical support. Co-I's Dr. Peter Blanchard and Prof. Ashley Villar are experts in supernova follow-up and will provide scientific and technical support. Stellar Physics and Stellar Types 6 false false false false false false SUPPORTED STAR GAMMA RAY BURSTER SUPERNOVA Expected magnitude based on supernova modeling. We have not been able to get ground-based imaging since March due to Sun constraint. J2000 EXT-STAR GAMMA RAY BURSTER SUPERNOVA A GRB SN at approximately z < 0.3 WFC3/UVIS Imaging No No F606W WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F606W WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F606W WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F606W WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F606W WFC3/IR Imaging No No F160W POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 1 false POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 3 false Timing link suitability includes constraints ([06 After 05 by at most 3.0 days]) The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. 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